This is an observational, prospective three-year longitudinal study. The investigators will enroll participants with primary neurogenic orthostatic hypotension. All participants will undergo an extensive neurological and cardiovascular evaluation, including detailed autonomic testing and quality of life assessment. The investigators will then determine the magnitude of the pressor effect produced by 18 mg atomoxetine given orally, measured 1 hour after drug administration. Participants will be followed annually or more often if there is a significant change in their clinical condition. During follow up at year 3, the investigators will repeat the initial neurological, cardiovascular and autonomic evaluation. The primary endpoint would be the final diagnosis made at year 3 after the initial evaluation (at the end of the follow-up period) or if they develop significant worsening of symptoms during follow-up phone assessments, based on specific clinical criteria.